Document FR-A-2 793 676 describes an illumination device which comprises a casing, in which a bulb and optical assemblies are arranged. Each optical assembly comprises a mirror and an aperture. The mirror is suitable for reflecting a light beam emitted by the bulb towards the aperture which is suitable for focusing the beam onto an illumination plane.
This device does not allow the size of the illumination spot to be varied for a given distance between the casing and the illumination plane.
There are further known illumination devices which allow the extent of the illumination spot to be varied by the mirror being tilted relative to the casing. However, these devices comprise a casing whose zones surrounding the apertures are opaque in order to ensure homogeneous illumination. These opaque zones lead to poor light output and an unattractive casing.
The object of the present invention is to overcome the disadvantages mentioned and to provide an assembly which allows the size of the illumination spot to be modified whilst still having good output.